thanks for the reply @lock042.
Sorry I think I’m not explaining correctly probably due to lack of knowledge or misinterpretation. When the fit is saved by siril it is being normalized in the range [0, 1] if the -output_norm parameter is given. When opening the file with another software (yes I’m talking about PI) the stats on normalized format is correctly represented. How the software knows that the data is already normalized in order to avoid another normalization when representing statistics in a normalized way?
Sorry again for the offtopic
PS: if you consider appropriate I can open a new thread or even close this one since I know I’m involving software not related with siril